1. Field of the Invention
This invention relates generally to an air conditioning apparatus employing a heat transfer medium for use in a vehicle having a large passenger area and, more particularly, but not by way of limitation, to an air conditioning apparatus having a vehicle engine driven compressor and a pair of electric motor driven compressors so that the passenger area may be cooled using either the engine driven compressor or one or both of the pair of motor driven compressors.
2. Description of the Prior Art
In general, air conditioning systems for vehicles having large passenger areas utilize either a single compressor driven by the engine of the vehicle or a separate electric motor driven compressor utilizing outside AC line voltage. However, systems of the first type place an unusually high burden on the engine of the vehicle, not only by the compressor itself but also by the condenser coil which is usually positioned in front of the engine thereby increasing the operating temperature of the engine. Systems of the latter type are only operative when connected to the AC line voltage thereby preventing the system from being used in transit. Even in systems utilizing both engine driven and motor driven compressors, such as the air conditioning systems described in the applicant's U.S. Pat. Nos. 3,885,398 and 3,984,224, described above, there is limited flexibility due to the presence of only one of each type of compressor.